API: Provide the HostConfig during "run".

Currently, the HostConfig is only passed from the CLI to Docker only
when issuing a docker create, but not when doing a docker run.

In the near future, in order to allocate ports at creation time rather
than start time, we will need to have the HostConfig readily available
at container creation.

This PR makes the client always pass the HostConfig when creating a
container (regardless of whether it's for a run or create).

Signed-off-by: Andrea Luzzardi <aluzzardi@gmail.com>